Sequential Injection Spectrophotometric Method for the Assay of Anti-inflammatory Diclofenac Sodium in Pharmaceutical Preparations

Abstract

The method developed in this study utilizes the SIA technique with spectrophotometric detection. Potassium permanganate is used as an oxidant in slightly acidic medium of 6.0 x 10 -6 mol L -1 sulfuric acid and the oxidized form of the drug is monitored spectrophotometrically at a wavelength of 450 nm for quantitative determination. The method has been validated and successfully applied to the assay of the compound formulated in pharmaceutical preparations. The calibration curve was linear within a range of 30 – 135 μg mL -1 with correlation coefficients of 0.998 and limits of detection (LOD) and limits of quantification (LOQ) of about 0.24 μg mL -1 and 0.7 μg mL -1 respectively. The method proved to be of high precision with a relative standard deviation (RSD) of about 1.5 %. Furthermore, the SIA method gave results for real samples (tablets) containing 50 μg mL -1 diclofenac sodium in good agreement with those obtained by the standard BP method. No statistical differences at the 95 % confidence level on applying the t-test were observed between the values obtained by the two methods. Thus, the proposed SIA method is reliable, faster than the standard BP potentiometric method and lends itself to automation. The advantages of the SIA technique and the newly adopted method over other conventional techniques and the reported existing standard methods such as rapidity, economy, and automation have been documented. The overall benefit of the SIA technique has also been highlighted.